Customer feeds back that the status of interface VLANIF 4003 on the S9300 changes between Up and Down frequently. As a result, service traffic is affected. According to the log, engineer found the CPU is very high during the problem so that transmission of LACP protocol packets times out. We successfully simulate the problem in the LAB because CPU high due to high quantity of ARP packets. According to the above analysis, we give suggestion as follows to customer.1、Enable the slow timeout mode for LACP to prevent the VLANIF interface being down if the transmission of LACP packets is delayed.[NNVGRD_AR05_S9303]Eth-Trunk2[NNVGRD_AR05_S9303-Eth-Trunk2]lacp timeout slow[NNVGRD_AR06_S9303]Eth-Trunk1[NNVGRD_AR06_S9303-Eth-Trunk1]lacp timeout slow2、The following operations can reduce the CPU usage if a lot of ARP packets are sent to the CPU or an ARP attack occurs. Configure ARP Miss suppression globally to prevent excessive ARP request packets at one time from one terminal.[NNVGRD_AR05_S9303]arp-miss speed-limit source-ip maximum 1[NNVGRD_AR06_S9303]arp-miss speed-limit source-ip maximum 13、Configure ARP Miss suppression in two super VLANs to reduce the number of ARP packets.[NNVGRD_AR05_S9303]inter Vlanif 950 [NNVGRD_AR05_S9303-Vlanif950]arp-miss suppress 30 [NNVGRD_AR05_S9303-Vlanif950]arp-miss suppress 30[NNVGRD_AR05_S9303]inter Vlanif 951 [NNVGRD_AR05_S9303-Vlanif951]arp-miss suppress 30[NNVGRD_AR05_S9303-Vlanif951]arp-miss suppress 30[NNVGRD_AR06_S9303]inter Vlanif 950 [NNVGRD_AR06_S9303-Vlanif950]arp-miss suppress 30[NNVGRD_AR06_S9303-Vlanif950]arp-miss suppress 30[NNVGRD_AR06_S9303]inter Vlanif 951 [NNVGRD_AR06_S9303-Vlanif951]arp-miss suppress 30[NNVGRD_AR06_S9303-Vlanif951]arp-miss suppress 30